Watching the new video. In my opinion it separates way more than is needs to. It's defiantly out of rebound travel and topped out. Compare the latest video to your earlier post with the rear axle hanging. Are the new shocks shorter at full extension than the old shocks? Separation is dictated by front pivot location. In your case the front spring eye. Without lowering or lengthening that point you can not reduce separation. Lowering the car will lower this point to the ground. But this is not a total cure as the center of gravity is now lower as well. The front eye mount needs to come down, NOT UP. Your only other alternative is to tighten the rebound slowing the separation. At this point air pressure and shock adjustments are a crutch to try and correct a instant center location that is to high and shocks topped out in rebound.
Doug

Question
#11 Yes, the distance between the tire and body. This separation presses the tire to the track. To much and too quick can overwhelm the tires ability to hook.
#2 Ok
#3 It is possible in some instances with leaf springs to still top out. The rear of the leaf bends, especially unclamped and can actually have greater travel than hanging static.
#4 Dropping the front of the spring will raise the car some. But it will reduce the tendency to separate because the instant center is lower.
#5 Being maxed out on rebound will not allow you to slow the separation any further without revalving. The fact that the compression is full tight may be contributing to the bounce after the initial hit. If its to stiff the tire cant come back into the body, thus it bounces.
#6 Stay here for the time being Get the back taken care of readdress the front after.

I think taking out some separation and loosening the rear compression would be a good 1st step.
Doug